Jaws used for applying clips, grasping, dissecting and otherwise manipulating tissue are known. They are generally formed in the multistep process of machining metal blanks.
Similarly, surgical stapling instruments are well known in the art. For example, U.S. Pat. Nos. 3,499,591; 3,490,675; and 3,079,606, all of which are incorporated by reference, describe surgical stapling instruments for applying multiple rows of metal staples sequentially to body tissue.
Typically, such instruments employ a metal anvil member to form or crimp the staples. The anvil member possesses an upper surface with staple crimping depressions, or "pockets." When the staples are driven into the anvil the legs of the staple enter the pockets and are crimped, thereby securing the body tissue.
The anvil member is generally machined from a surgically acceptable strong metal alloy such as stainless steel. Then the staple pockets generally are coined into the finished anvil with a press. Finally the pockets are coated to make the pocket more suitable for interaction with the staple. This is an expensive multistep procedure which is not without fallouts in manufacturing anvils.
Alternatively, the pockets may be formed by electrical discharge machining. This process involves burning the pockets into the anvil with a copper electrode. This too is an extremely cost inefficient process. In order for the electrode to burn the pocket in the blank anvil, the electrode must be heated to a temperature that also causes the electrode itself to burn, requiring a new electrode for every anvil manufactured.
An anvil typically experiences pronounced forces when staples are advanced into contact with the staple forming surface thereof Anvils adapted for use with linear staplers of the type disclosed in U.S. Pat. No. 3,490,675, for example, may tend to bend, splay or otherwise move out of cooperative alignment with the staple cartridge in response to such forces. Steps have been taken to strengthen the anvils to resist such forces, e.g., by increasing wall thicknesses and the like, and/or to provide alignment means as described in U.S. Pat. No. 5,014,899.
However, the options available to manufacturers of surgical staplers which employ anvils become even more limited when the stapler is adapted for endoscopic use. In such cases, the anvil must be configured and dimensioned to pass through an endoscopic guide tube which typically has an inside diameter of 5 to 15 mm. Thus, the anvil typically exhibits a half-moon cross section and may be adapted to form one or more staple lines, e.g., from 15 to 60 mm in length. Such anvils must exhibit tremendous strength and be manufactured to close tolerances.